This invention relates to an oil-cooled valve adapted for use in an internal combustion engine.
Diesel engines operating on high sulfur fuels, oftentimes containing vanadium compounds, periodically require "top end overhauls" or grinding of the exhaust valves employed therein due to corrosion effects and high heat levels imposed on the valve faces. Such corrosion tends to induce a "channeling" or "guttering" of the valve faces to accelerate corrosion and to give rise to gas leakage past the valves and potential breakage of the valve heads. Such corrosion also occurs on the top of the valve heads which tends to cause severe pitting which may also lead to valve head failures.
Metallurgical solutions have not fully solved the corrosion problem due to the high temperature levels experienced by the valves during operation thereof. Therefore, the state of the art has experienced various attempts to cool such exhaust valves by packing them with metallic sodium or other suitable cooling medium or by circulating oil through the valves. The former attempt has a tendency, for example, to raise the temperature level of the valve stems to thus reduce the service life of the tubular guides reciprocally mounting the valves in an engine.
Also, circulation of oil through the valves for cooling purposes has not provided a final solution to the corrosion problem. In particular, it has proven difficult with conventional valve arrangements of this type to communicate the cooling oil in close proximity to the valve faces whereat the greatest amount of heat dissipation is required. In this connection, the cooling oil communicated to the head of the valve is at least partially trapped thereat to thus prevent a continuous flow and efficient distribution of the cooling oil to the critical surface areas of the valve.
In addition to the corrosion problem, a conventional valve of the latter type, such as that disclosed in U.S. Pat. No. 3,911,875, may have a tube disposed in a hollow stem thereof which tends to vibrate during engine operation. This patent apparently discloses one solution to the vibratory problem by interposing a support piece between the valve stem proper and the tube which is adapted to communicate cooling oil therethrough.